# Thread: Extraction of records at specific time interval

1. Registered User
Join Date
Sep 2003
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WA, USA
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## Unanswered: Extraction of records at specific time interval

I have a large volume of data that was recorded every second.
I want to extract data from the database every "x" number of seconds.
i.e. SELECT * FROM data WHERE time = (every 30 seconds);

The goal is to reduce the data set down to a number of records over time at an interval determined by the user.

I have in mind a javascript dialog asking the user for the time interval, this passes the value to a PHP program that loops the SQL query, incrementing the time='x' value each time by the interval value and writing the results to screen/file.

Any ideas or ways to do this directly in SQL?

Thank you,
BK_Ziv

2. Registered User
Join Date
Sep 2003
Posts
1

SELECT * FROM data WHERE time % 30 = 0

I'm not sure if that would actually work in mysql , but that expression is the simplest way to explain it

the other option is to do some calculations (with php I assume) before the data is inserted, and determine if the time fits any time patterns. You could have columns to show if the time matches a 2 second, 3 second, 4 second, 5 second, 7 second or 9 second interval.

So if \$time % 2 = 0 , you insert a '1' for the 2second column, if it doesnt you insert a 0 , same for all other intervals.

And then to get all data that matches the 30 second frequency...

SELECT * FROM data WHERE 2second = 1 AND 3second = 1 AND 5second = 1

2 * 3 * 5 = 30 , so any data matching those 3 columns must have a 30 second frequency.

With those 6 values you could make most combinations for all the frequencys you want to show.

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